Camera animation caused the camera disappeared
Check that you camera is not hidden and it is on visible layer.

And also you can try this:


  Its easy to just delete the camera and create a new one but in this
  case I will lose my animation already applied on camera.


You will not lose animation because block with animation data will not delete with object.

So you can do this:

Open dope sheet in action editor mode



Find name of camera animation data:



When delete camera and create new one. And select animation data of your deleted camera: